Program evaluation within health care research is a common practice, and many program evaluation methods and data collection instruments have been developed and empirically tested. However, program evaluation of substance abuse intervention is a relatively new science, especially when it comes to estimating economic costs and benefits. Given the great need for economic evaluation studies in the substance abuse literature, the proposed application will accomplish the following broad aims: 1. Examine the use and applicability of the current Addiction Severity Index (ASI) for economic evaluation of addiction services, investigate the use of additional economically relevant items for the ASI-6 and develop methods to value ASI items so that clinical information can be combined with financial information from the Drug Abuse Treatment Cost Analysis Program (DATCAP) as part of a benefit-cost analysis. 2. Examine the use and applicability of the current Treatment Services Review (TSR) as a data collection tool for estimating the cost of addiction and ancillary services for individual patients, add economically relevant items to the TSR-6, and develop methods to combine data from the ASI and TSR to estimate the economic benefits and costs of addiction treatment of individual patients. 3. Test the practicality and scientific integrity of using the ASI, TSR, and DATCAP in benefit-cost analyses of addiction services by adding an economic evaluation component to state-level treatment assessments that are currently being conducted in Texas, Virginia, and Washington. The proposed study expands on the economic component of the University of Pennsylvania Center for Instruments and Measures Development, which tested the reliability the validity of the DATCAP instrument. The proposed research seeks to combine the cost data as collected through the DATCAP instrument with clinical proposed research seeks to combine the cost data as collected through the DATCAP instrument with clinical information from the ASI and TSR instruments. Since the ASI and TSR are used extensively by treatment programs in the U.S. as well as abroad, this study holds great potential to assist researchers and program directors with economic evaluation guidelines.